Light output control device, illumination system, and facility apparatus

ABSTRACT

A light output control device includes a switching device, multiple signal input ports, a signal selection circuit, and a control circuit. The switching device is to be electrically connected between a direct-current power supply and a light source circuit. The light source circuit includes a semiconductor light emitting element. The multiple signal input ports respectively correspond to multiple kinds of light output control signals. The signal selection circuit selects, when receiving two or more light output control signals indicating different light output levels through the multiple signal input ports, a light output control signal indicating a lowest (or highest) light output level, from the two or more light output control signals. The control circuit performs switching control of the switching device with a duty cycle corresponding to the lowest (or highest) light output level indicated by the light output control signal selected by the signal selecting circuit.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based upon and claims the benefit of priorityof Japanese Patent Application No. 2015-165999, filed on Aug. 25, 2015,the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to light output controldevices, illumination systems, and facility apparatuses, andparticularly to a light output control device for lighting asemiconductor light emitting element with a desired light output level,and an illumination system and a facility apparatus including the same.

BACKGROUND ART

There has been proposed a light emitting diode (LED) power supply devicethat can adjust the brightness and the color temperature of lightemitted from an LED module (JP 2012-226924 A, hereinafter referred to asDocument 1). The LED power supply device of Document 1 includes the LEDmodule and a power supply device. The LED module includes a first lightemitting unit for emitting first color light and a second light emittingunit for emitting second color light. The power supply device suppliesan electric current to cause the LED module to emit light. The powersupply device includes a constant current output circuit, a colortemperature control circuit, and a control circuit. The control circuitreceives a light output control signal and a color temperature signalfrom an external dimmer. The light output control signal is a pulsewidth modulation (PWM) signal, and indicates a desired brightness by theduty cycle. The color temperature signal is a PWM signal, and indicatesa desired color temperature by the duty cycle. The control circuitadjusts the brightness (light output) of the LED module by controllingthe current outputted from the constant current output circuit based onthe light output control signal. Also, the control circuit adjusts thecolor temperature of light emitted from the LED module by controlling ablinking cycle of the first light emitting unit and a blinking cycle ofthe second light emitting unit based on the color temperature signal.

The LED power supply device disclosed in Document 1 can receive andhandle the light output control signal represented by the PWM signalindicating a desired brightness by the duty cycle. However, the LEDpower supply device of Document 1 cannot handle the light output controlsignal represented by a signal other than the PWM signal. That is, theLED power supply device of Document 1 cannot cooperate with a dimmerthat outputs a light output control signal represented by a signal otherthan the PWM signal.

SUMMARY

An objective of the present disclosure is to provide a light outputcontrol device, an illumination system, and a facility apparatus capableof handling multiple kinds of light output control signals.

A light output control device according to an aspect of the presentdisclosure includes a switching device, multiple signal input ports, asignal selection circuit, and a control circuit. The switching device isto be electrically connected between a direct-current power supply and alight source circuit. The light source circuit includes a semiconductorlight emitting element. The multiple signal input ports respectivelycorrespond to multiple kinds of light output control signals. The signalselection circuit is configured to, when receiving two or more lightoutput control signals indicating different light output levels throughthe multiple signal input ports, select a light output control signalindicating a lowest light output level, from the two or more lightoutput control signals. The control circuit is configured to performswitching control of the switching device with a duty cyclecorresponding to the lowest light output level indicated by the lightoutput control signal selected by the signal selecting circuit.

A light output control device according to another aspect of the presentdisclosure includes a switching device, multiple signal input ports, asignal selection circuit, and a control circuit. The switching device isto be electrically connected between a direct-current power supply and alight source circuit. The light source circuit includes a semiconductorlight emitting element. The multiple signal input ports respectivelycorrespond to multiple kinds of light output control signals. The signalselection circuit is configured to, when receiving two or more lightoutput control signals indicating different light output levels throughthe multiple signal input ports, select a light output control signalindicating a highest light output level, from the two or more lightoutput control signals. The control circuit is configured to performswitching control of the switching device with a duty cyclecorresponding to the highest light output level indicated by the lightoutput control signal selected by the signal selecting circuit.

An illumination system according to another aspect of the presentdisclosure includes any of the light output control devices of theabove, and the light source circuit including the semiconductor lightemitting element.

A facility apparatus according to another aspect of the presentdisclosure includes any of the light output control devices of theabove, the light source circuit including the semiconductor lightemitting element, and the facility apparatus body that holds the lightsource circuit and the light output control device.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures depict one or more implementations in accordance with thepresent teaching, by way of example only, not by way of limitations. Inthe figures, like reference numerals refer to the same or similarelements.

FIG. 1 is a circuit diagram of an illumination system according toEmbodiment 1 of the present disclosure.

FIG. 2 is a schematic configuration diagram of the illumination system.

FIG. 3 is a circuit diagram of a signal selection circuit in a lightoutput control device according to Embodiment 1.

FIG. 4A is a graph illustrating a relation between a desired lightoutput and a duty cycle according to a light output control signal S1 ofthe light output control device of Embodiment 1. FIG. 4B is a graphillustrating a relation between a desired light output and a voltagelevel according to a light output control signal S2 of the light outputcontrol device of Embodiment 1.

FIG. 5A is a graph illustrating a time variation of the duty cycle ofthe light output control signal S1 and the voltage level of the lightoutput control signal S2 according to an operation example of the signalselection circuit. FIG. 5B is a graph illustrating a time variation of adesired light output indicated by a light output control signal S3generated by the signal selection circuit according to the operationexample.

FIG. 6 is a perspective view of the light output control device.

FIG. 7 is an exploded perspective view of the light output controldevice.

FIG. 8 is a plan view of a circuit board of the light output controldevice.

FIG. 9 is a circuit diagram of a signal selection circuit in a lightoutput control device according to Embodiment 2 of the presentdisclosure.

FIG. 10A is a graph illustrating a relation between a desired lightoutput and a duty cycle according to a light output control signal S1 ofthe light output control device of Embodiment 2. FIG. 10B is a graphillustrating a relation between a desired light output and a voltagelevel according to a light output control signal S2 of the light outputcontrol device of Embodiment 2.

FIG. 11A is a graph illustrating a time variation of the duty cycle ofthe light output control signal S1 and the voltage level of the lightoutput control signal S2 according to an operation example of the signalselection circuit. FIG. 11B is a graph illustrating a time variation ofa desired light output indicated by a light output control signal S3generated by the signal selection circuit according to the operationexample.

FIG. 12A is a perspective view of a facility apparatus according toEmbodiment 3 of the present disclosure. FIG. 12B is a perspective viewof a facility apparatus according to a modification of Embodiment 3.

DETAILED DESCRIPTION

Embodiments 1 to 3 described hereinafter are given as examples ofembodiments of the present disclosure, and the embodiments of thepresent disclosure are not limited to Embodiments 1 to 3 describedbelow. Embodiments 1 to 3 can be modified appropriately in their designsand the like as long as the modifications can achieve the object of thepresent disclosure.

Embodiment 1

A light output control device and an illumination system according toEmbodiment 1 will be explained with reference to FIG. 1 to FIG. 8.

(1.1) Structure of Illumination System

FIG. 1 is a circuit diagram of the illumination system. FIG. 2 is aschematic configuration diagram of the illumination system.

The illumination system of the present embodiment includes adirect-current (DC) power supply 1, a light output control device 2, anda light source circuit 3. In the illumination system of the presentembodiment, the light output control device 2 is connected between theDC power supply 1 and the light source circuit 3. The light outputcontrol device 2 is connected to the light source circuit 3 throughelectric wires W1. The light output control device 2 is connected to theDC power supply 1 through electric wires W2. The light output controldevice 2 is connected to an external dimmer 4 through electric wires W3,and is connected to a relay circuit 5 through electric wires W4.

The DC power supply 1 converts an AC voltage inputted from an AC powersupply 100 such as a commercial power supply (for example, AC voltage ina range of 100 to 242 V) into a constant DC voltage and outputs theresultant DC voltage. The DC power supply 1 may be a known switchingregulator. The DC power supply 1 outputs a DC voltage having a voltagevalue (DC 24 V, for example) allowing the light source circuit 3 tolight.

The light source circuit 3 includes seven light emitting diodes 311 to317 each of which is a semiconductor light emitting element, a constantcurrent circuit 32, and a diode 33 for preventing reverse current. Theconstant current circuit 32 keeps the current flowing through the lightemitting diodes 311 to 317 constant. The constant current circuit 32includes NPN transistors 321 and 322, and resistors 323 to 326. Thelight source circuit 3 includes the light emitting diodes 311 to 317serving as the semiconductor light emitting elements, but is not limitedthereto. For example, the light source circuit 3 may include, as thesemiconductor light emitting element, an organic electro luminescence(EL) element(s) or the like, instead of the light emitting diodes 311 to317.

The light source circuit 3 includes a pair of connection terminals 301and 302. The positive electrode side connection terminal 301 isconnected to an anode of the diode 33. The diode 33 has a cathodeconnected to a collector of the transistor 321 through the resistor 323.The transistor 321 has an emitter connected to the negative electrodeside connection terminal 302. The collector of the transistor 321 isalso connected to a base of the transistor 322 through the resistor 324.The transistor 322 has an emitter connected to a base of the transistor321. The resistors 325 and 326 are connected in parallel to form aparallel circuit which is connected between the emitter of thetransistor 322 and the emitter of the transistor 321. The seven lightemitting diodes 311 to 317 are connected in series between the cathodeof the diode 33 and a collector of the transistor 322 so as to allow acurrent to flow in a direction same as a direction in which the currentflow through the diode 33.

The light output control device 2 includes a switching device 21,resistors 22, 23 and 29, a control circuit 24, a signal selectioncircuit 25, and a power supply circuit 28. The control circuit 24includes a pulse width modulation (PWM) signal generation circuit 26 anda drive circuit 27.

The light output control device 2 includes a power supply connectionport 210, a light source connection port 220, and two signal input ports230 and 240. The power supply connection port 210 is connected to the DCpower supply 1. Specifically, the power supply connection port 210includes a pair of connection terminals 211 and 212. The connectionterminal 211 is connected to a positive electrode side output terminalof the DC power supply 1. The connection terminal 212 is connected to anegative electrode side output terminal of the DC power supply 1. Thelight source connection port 220 is connected to the light sourcecircuit 3. Specifically, the light source connection port 220 includes apair of connection terminals 221 and 222. The positive electrode sideconnection terminal 221 is connected to the connection terminal 301 ofthe light source circuit 3. The negative electrode side connectionterminal 222 is connected to the connection terminal 302 of the lightsource circuit 3.

Different kinds of light output control signals are inputted to the twosignal input ports 230 and 240. For example, the dimmer 4 is connectedto the signal input port 230. The signal input port 230 receives a lightoutput control signal (first kind of light output control signal) S1from the dimmer 4. The light output control signal S1 is a PWM signalhaving a duty cycle corresponding to a desired light output level. Forexample, the relay circuit 5 is connected to the signal input port 240.The signal input port 240 receives a light output control signal (secondkind of light output control signal) S2. The light output control signalS2 is a voltage signal with a voltage level indicative of either of twolevels in accordance with whether a relay of the relay circuit 5 is onor off, for example. In a specific example, the relay circuit 5includes: a first resistor (not shown) connected between a pair ofterminals of the signal input port 240; a second resistor (not shown)and a DC power supply (not shown) connected in series to form a seriescircuit connected between both ends of the first resistor; and the relayconnected between both ends of the second resistor. The different kindsof light output control signals means light output control signalshaving different kinds of parameters indicating the desired light outputlevel. In the present embodiment, the parameter of the light outputcontrol signal S1 is the duty ratio of the PWM signal, and the parameterof the light output control signal S2 is the voltage level of thevoltage signal. In other words, the different kinds of light outputcontrol signals indicate the desired light output levels in differentmanners (e.g., by use of different kinds of parameters).

The connection terminal 211 and the connection terminal 221 areelectrically connected to each other through the resistor 29.

The switching device 21 is a metal oxide semiconductor field effecttransistor (MOSFET) for example, and has a drain connected to theconnection terminal 222. The switching device 21 has a source connectedto the connection terminal 212. The resistor 23 is connected between agate and the source of the switching device 21. The switching device 21is not limited to the MOSFET, but may be a junction field effecttransistor (JFET) or a bipolar transistor such as an insulated gatebipolar transistor (IGBT).

The signal selection circuit 25 is connected to the two signal inputports 230 and 240. The signal selection circuit 25 receives the lightoutput control signal S1 from the dimmer 4 and the light output controlsignal S2 from the relay circuit 5.

Hereinafter, a circuit structure of the signal selection circuit 25 isexplained based on a circuit diagram of FIG. 3. The circuit structure ofthe signal selection circuit 25 shown in FIG. 3 is one example, and thecircuit structure of the signal selection circuit 25 is not limited tothat shown in FIG. 3.

The signal selection circuit 25 includes a first conversion circuit 40,a second conversion circuit 50, a lower limit setting circuit 60, and azener diode 70 for setting an upper limit.

The first conversion circuit 40 includes a resistor 41 and a capacitor42, and functions as an integration circuit. The first conversioncircuit 40 receives the light output control signal S1 through thesignal input port 230 and smooths the light output control signal S1. Asa result, the first conversion circuit 40 outputs a DC voltage having avoltage value corresponding to a duty cycle of the light output controlsignal S1. The first conversion circuit 40 has an output end connectedto an output end P1 of the signal selection circuit 25. That is, thefirst conversion circuit 40 is configured to convert the light outputcontrol signal S1 into a conversion value which is represented by aphysical amount and has a magnitude (voltage value) corresponding to alight output level indicated by the light output control signal S1.Specifically, the first conversion circuit 40 is configured to convert aPWM signal serving as the light output control signal S1 into aconversion value which is represented by a DC voltage and has a voltagevalue corresponding to a duty cycle of the light output control signalS1.

In the embodiment, the light output control signal S1 is a PWM signalhaving a duty cycle corresponding to a setting value for light outputlevel of the light source circuit 3. In the embodiment, the settingvalue for light output level means a desired light output level of thelight source circuit 3, and is expressed in percentage. For example,when the setting value for light output level is 100%, the light sourcecircuit 3 emits light with a light output equal to a light output oflight emitted when the light source circuit 3 is supplied with a ratedcurrent. That is, the light output level of the light source circuit 3when the rated current is supplied to the light source circuit 3 isdefined as 100%. For example, when the setting value for light outputlevel is 0%, the light source circuit 3 is turned off (does not emitlight). That is, the light output level of the light source circuit 3when the light source circuit 3 is turned off is defined as 0%.

The light output control signal S1 of the present embodiment is definedso that the minimum of the magnitude (duty cycle) of the light outputcontrol signal S1 corresponds to the maximum of the setting value forlight output level. FIG. 4A is a graph illustrating a relation betweenthe setting value for light output level (desired light output) and theduty cycle of the light output control signal S1. The setting value forlight output level decreases in direct proportion to the duty cycle ofthe light output control signal S1. Therefore, the setting value forlight output level decreases and also the light output of the lightsource circuit 3 decreases with an increase in the duty cycle of thelight output control signal S1.

In short, with regard to the light output control signal S1 (in otherwords, when only the light output control signal S1 is inputted to thelight output control device 2), the light output control device 2decreases the setting value for light output level with an increase inthe duty cycle of the light output control signal S1.

In the example of FIG. 4A, the setting value for light output levelchanges linearly with respect to the duty cycle of the light outputcontrol signal S1, but the light output control signal S1 is not limitedto this. The setting value for light output level may change nonlinearlywith respect to the duty cycle of the light output control signal S1, aslong as the setting value for light output level decreases with anincrease in the duty cycle. It should be noted that the lower limit ofthe desired light output may be limited, by the lower limit settingcircuit 60, to a lower limit value Lmin. The upper limit of the desiredlight output may be limited, by the zener diode 70, to 100% (see FIG.4A). In the example of FIG. 4A, the light output control signal S1 witha duty cycle ranging from 0% to DT1% indicates the desired light outputlevel of 100%. The light output control signal S1 with a duty cycleranging from DT2% to 100% indicates the desired light output level ofLmin %.

The first conversion circuit 40 serving as the integration circuit has acut-off frequency sufficiently lower than a frequency of the PWM signalof the light output control signal S1. Therefore, when the PWM signal asthe light output control signal S1 is supplied, the first conversioncircuit 40 outputs a DC voltage V1 having a voltage value correspondingto the duty cycle of the light output control signal S1. The voltagevalue of the DC voltage V1 increases in proportion to the duty cycle ofthe light output control signal S1.

The second conversion circuit 50 includes an NPN transistor 51,resistors 52 to 54, an operation amplifier 55, and a diode 56. Theoperation amplifier 55 has a non-inverting input terminal connected to aconnection point of the resistors 53 and 54. The resistors 53 and 54constitute a voltage divider circuit. The voltage divider circuit of theresistors 53 and 54 has a high voltage side terminal to which a constantDC voltage Vcc is supplied from the power supply circuit 28. The voltagedivider circuit of the resistors 53 and 54 has a low voltage sideterminal connected to a collector of the transistor 51. The transistor51 has an emitter connected to a ground of the signal selection circuit25. The transistor 51 has a base connected to the signal input port 240through the resistor 52. The operation amplifier 55 has an outputterminal connected to a cathode of the diode 56. The operation amplifier55 has an inverting input terminal connected to an anode of the diode56. The anode of the diode 56 is also connected to the output end P1 ofthe signal selection circuit 25. The diode 56 is connected between theoutput terminal of the operation amplifier 55 and the output end P1 soas to allow a current to flow in a direction from the output end P1 tothe output terminal of the operation amplifier 55. Therefore, when avoltage value of the output voltage V1 of the first conversion circuit40 is equal to or greater than a voltage value of an output voltage V2of the operation amplifier 55, the second conversion circuit 50 holds(clamps) the voltage value of the output end P1 to the voltage value ofthe output voltage V2 of the operation amplifier 55.

In the embodiment, the light output control signal S2 supplied to thesignal input port 240 is a voltage signal with a voltage levelindicative of either of two levels in accordance with whether the relayof the relay circuit 5 is on or off. The light output control signal S2of the present embodiment is defined so that the minimum of themagnitude (voltage level) of the light output control signal S2corresponds to the maximum of the setting value for light output levelfor the light source circuit 3. FIG. 4B is a graph illustrating arelation between the light output level (desired light output) and thevoltage level of the light output control signal S2. The light outputcontrol signal S2 with the voltage level lower than threshold Vth1indicates the setting value of 100% for light output level. The lightoutput control signal S2 with the voltage level equal to or higher thanthe threshold Vth1 indicates the setting value of L1% for light outputlevel.

In the present embodiment, when the relay is turned on, the light outputcontrol signal S2 has a voltage level of VS1 (<Vth1), and the outputvoltage V2 of the operation amplifier 55 of the second conversioncircuit 50 thus has a voltage value indicating the setting value of 100%for light output level. A state in which the light source circuit 3emits light with a light output level of 100% may be referred to as“full-lighting state”.

When the relay is turned off, the light output control signal S2 has avoltage level of VS2 (>Vth1), and the output voltage V2 of the operationamplifier 55 of the second conversion circuit 50 thus has a voltagevalue indicating the setting value of L1% for light output level. In theexample of FIG. 4B, the setting value for light output level is switchedbetween L1% and 100% depending on whether the voltage level of the lightoutput control signal S2 is lower or higher than the threshold Vth1.

That is, the second conversion circuit 50 is configured to convert thelight output control signal S2 into a conversion value which isrepresented by a physical amount and has a magnitude (voltage value)corresponding to a light output level indicated by the light outputcontrol signal S2. The second conversion circuit 50 is configured toconvert the voltage signal of which voltage level is any of two or morelevels serving as the light output control signal S2 into a conversionvalue which is represented by a DC voltage and has a voltage valuecorresponding to the voltage level of the light output control signalS2. Specifically, in the present embodiment, the second conversioncircuit 50 is configured to convert the voltage signal of which voltagelevel is either of two levels serving as the light output control signalS2 into a conversion value which is represented by a DC voltage and hasa voltage value corresponding to the voltage level of the light outputcontrol signal S2.

In the present embodiment, the voltage level of the light output controlsignal S2 is either of the first level VS1 and the second level VS2higher than the first level VS1. The setting value for light outputlevel (100%) corresponding to the first level VS1 is greater than thesetting value for light output level (L1%) corresponding to the secondlevel VS2.

In short, with regard to the light output control signal S2 (in otherwords, when only the light output control signal S2 is inputted to thelight output control device 2), the light output control device 2 setsthe setting value for light output level to a first setting value whenthe voltage level of the light output control signal S2 is lower than athreshold, and sets the setting value for light output level to a secondsetting value smaller than the first setting value when the voltagelevel of the light output control signal S2 is equal to or greater thanthe threshold.

Note that, there may be a hysteresis width between the threshold for thelight output control signal S2 for determining whether to change thesetting value for light output level from 100% to L1% and the thresholdfor the light output control signal S2 for determining whether to changethe setting value for light output level from L1% to 100%.

The lower limit setting circuit 60 includes resistors 61 and 62constituting a voltage divider circuit, an operation amplifier 63, and adiode 64. The power supply circuit 28 applies a constant DC voltage Vccto a series circuit of the resistors 61 and 62. The voltage dividercircuit of the resistors 61 and 62 generates a divided voltage having avoltage value of Vmin. The divided voltage is inputted to anon-inverting input terminal of the operation amplifier 63. The diode 64has an anode connected to an output terminal of the operation amplifier63. The diode 64 has a cathode connected to an inverting input terminalof the operation amplifier 63 and the output end P1 of the signalselection circuit 25. The diode 64 is connected between the outputterminal of the operation amplifier 63 and the output end P1 so as toallow a current to flow in a direction from the output terminal of theoperation amplifier 63 to the output end Pl. Therefore, the lower limitsetting circuit 60 keeps the lower limit of the voltage of the outputend P1 not lower than the voltage value Vmin. In other words, the lowerlimit of a light output control signal S3 outputted from the signalselection circuit 25 is limited to the voltage value Vmin (the voltagelevel of the light output control signal S3 is kept equal to or higherthan the voltage value Vmin).

The zener diode 70 has a cathode connected to the output end P1 of thesignal selection circuit 25. The zener diode 70 has an anode connectedto the ground of the signal selection circuit 25. Even when at lease oneof the output voltage of the first conversion circuit 40 and the outputvoltage of the second conversion circuit 50 exceeds the zener voltageVZ1 of the zener diode 70, the voltage of the output end P1 is clampedto the zener voltage VZ1 by the zener diode 70. In other words, theupper limit of the light output control signal S3 outputted from thesignal selection circuit 25 is limited to the zener voltage VZ1 (thevoltage level of the light output control signal S3 is kept equal to orless than the zener voltage VZ1).

When the output voltage V1 of the first conversion circuit 40 becomeslower than the voltage value Vmin, the diode 64 of the lower limitsetting circuit 60 allows a current to pass therethrough, and as aresult the voltage of the output end P1 is kept at the voltage valueVmin. When the output voltage V1 of the first conversion circuit 40and/or the output voltage V2 of the operation amplifier 55 of the secondconversion circuit 50 become higher than the zener voltage VZ1, thevoltage of the output end P1 is kept at the zener voltage VZ1 by thezener diode 70. When both the output voltages V1 and V2 are equal to orhigher than the voltage value Vmin and also equal to or lower than thezener voltage VZ1, the voltage value of the light output control signalS3 of the signal selection circuit 25 corresponds to the smaller one ofthe output voltage V1 and the output voltage V2.

The control circuit 24 includes the PWM signal generation circuit 26 andthe drive circuit 27.

The PWM signal generation circuit 26 includes a microcomputer, forexample. The microcomputer executes programs stored in a read onlymemory (ROM) for example to perform PWM control of the switching device21. The PWM signal generation circuit 26 generates a PWM signal S4 ofwhich duty cycle varies in accordance with the light output controlsignal S3 supplied from the signal selection circuit 25, and outputs thegenerated PWM signal S4 to the drive circuit 27.

The drive circuit 27 has an output terminal connected to a first end ofthe resistor 22. The resistor 22 has a second end connected to a gate ofthe switching device 21. The drive circuit 27 performs switching controlof the switching device 21 in accordance with a signal level of the PWMsignal S4 supplied from the PWM signal generation circuit 26. Forexample, the drive circuit 27 turns on the switching device 21 when thesignal level of the PWM signal S4 indicates a high level. The drivecircuit 27 turns off the switching device 21 when the signal level ofthe PWM signal S4 indicates a low level.

The power supply circuit 28 converts the DC voltage having a certainvoltage value (DC 24 V, for example) supplied from the DC power supply 1into a DC voltage having a desired voltage value (DC 12 V, for example),and supplies the resultant DC voltage to the control circuit 24 and thesignal selection circuit 25 (as an operating voltage).

(1.2) Explanation of Operations

Hereinafter, operations of the illumination system will be exampled.

(1.2.1) Operations of Signal Selection Circuit 25

The following explanation referring to FIG. 5A and FIG. 5B relates to anoperation of the signal selection circuit 25 with the signal input port230 and the signal input port 240 respectively receiving the lightoutput control signal S1 from the dimmer 4 and the light output controlsignal S2 from the relay circuit 5.

In a period from a time point t0 to a time point t2, the relay is turnedon, and the light output control signal S2 has the first level VS1. Inthis period, the light output level indicated by the light outputcontrol signal S2 is 100%. In a period after the time point t2, therelay is turned off, and the light output control signal S2 has thesecond level VS2. In this period, the light output level indicated bythe light output control signal S2 is L1%.

At the time point t0, the duty cycle of the light output control signalS1 is set to 100%. The duty cycle of the light output control signal S1gradually decreases over time in a period between the time point t0 anda time point t3. The duty cycle of the light output control signal S1reaches 0% at the time point t3. Therefore, the light output levelindicated by the light output control signal S1 is Lmin % at the timepoint t0, and increases from Lmin % to 100% with a lapse of time fromthe time point t0 to the time point t3.

In the period from the time point t0 to the time point t2, the lightoutput level indicated by the light output control signal S2 is lowerthan the light output level indicated by the light output control signalS1. In this case, the voltage value of the output voltage V1 of thefirst conversion circuit 40 is greater than the voltage value of theoutput voltage V2 of the second conversion circuit 50, and as a resultthe voltage value of the output end P1 of the signal selection circuit25 is set to the voltage value of the output voltage V1 of the firstconversion circuit 40. That is, the signal selection circuit 25 selectsthe light output control signal S1, which indicates a lower light outputlevel of the light output control signals S1 and S2, and generates thelight output control signal S3 in accordance with the light outputcontrol signal S1, and outputs the light output control signal S3 to thePWM signal generation circuit 26. In a period from the time point t0 toa time point t1, the voltage value of the output voltage V1 of the firstconversion circuit 40 is smaller than the voltage value Vmin of thelower limit setting circuit 60, and thus the light output control signalS3 is set to a voltage value corresponding to the lower limit Lmin ofthe light output level. In a period from the time point t1 to the timepoint t2, the voltage value of the output voltage V1 of the firstconversion circuit 40 is greater than the voltage value Vmin of thelower limit setting circuit 60, and thus the light output control signalS3 is set to a voltage value corresponding to the output voltage V1 ofthe first conversion circuit 40.

The relay is turned off at the time point t2. In the period after thetime point t2, the light output level indicated by the light outputcontrol signal S2 is higher than the light output level indicated by thelight output control signal S1. In this case, the voltage value of theoutput voltage V2 of the second conversion circuit 50 is greater thanthe voltage value of the output voltage V1 of the first conversioncircuit 40, and as a result the voltage value of the output end P1 ofthe signal selection circuit 25 is set to the voltage value of theoutput voltage V2 of the second conversion circuit 50. That is, thesignal selection circuit 25 selects the light output control signal S2,which indicates a lower light output level of the light output controlsignals S1 and S2, and outputs a signal corresponding to the lightoutput control signal S2. The light output control signal S3 of thesignal selection circuit 25 has a voltage value corresponding to thelight output control signal S2.

In summary, when the two light output control signals S1 and S2 areinputted to the signal selection circuit 25, the signal selectioncircuit 25 selects a light output control signal indicating a lowerlight output level from the two light output control signals S1 and S2.

In the explanation above, the two light output control signals S1 and S2are both inputted to the signal selection circuit 25, but either one ofthe light output control signals S1 and S2 alone may be inputted to thesignal selection circuit 25.

For example, the following explanation relates to an operation of thesignal selection circuit 25 in a case where the light output controlsignal S1 is supplied to the signal input port 230 but the light outputcontrol signals S2 is not supplied to the signal input port 240. Whenthe light output control signal S2 is not supplied to the signal inputport 240, the voltage level of the signal input port 240 is lower thanthe threshold Vth1. Therefore, the output voltage V2 of the operationamplifier 55 of the second conversion circuit 50 has a voltage valueindicating the setting value of 100% for light output level. In thiscase, the signal selection circuit 25 selects the output voltage V1,which indicates a lower light output level, from the output voltages V1and V2, and the signal selection circuit 25 outputs the light outputcontrol signal S3 having a voltage value corresponding to the lightoutput control signal S1.

The following explanation relates to an operation of the signalselection circuit 25 in another case where the light output controlsignal S2 is supplied to the signal input port 240 but the light outputcontrol signals S1 is not supplied to the signal input port 230. It isconsidered that a situation where the light output control signal S1 isnot supplied to the signal input port 230 is equivalent to a situationwhere the light output control signal S1 having a duty cycle of 0% issupplied. Therefore, the output voltage V1 of the first conversioncircuit 40 has a voltage value indicating the setting value of 100% forlight output level. In this case, the signal selection circuit 25selects the output voltage V2, which indicates a lower light outputlevel, from the output voltages V1 and V2, and the signal selectioncircuit 25 outputs the light output control signal S3 having a voltagevalue corresponding to the light output control signal S2.

(1.2.2) Operation of Control Circuit 24

When the light output control signal S3 is supplied from the signalselection circuit 25 to the PWM signal generation circuit 26 of thecontrol circuit 24, the PWM signal generation circuit 26 generates thePWM signal S4 having a duty cycle corresponding to the voltage level ofthe light output control signal S3.

The PWM signal generation circuit 26 outputs the PWM signal S4 to thedrive circuit 27.

The drive circuit 27 performs the switching control of the switchingdevice 21 in accordance with the PWM signal S4. As a result of theswitching operation of the switching device 21, the DC voltage suppliedfrom the DC power supply 1 is converted into a rectangular wave voltagehaving an amplitude equal to the voltage value of the DC voltage. Therectangular wave voltage is applied to the light source circuit 3. Forexample, the drive circuit 27 turns on the switching device 21 during aperiod in which the signal level of the PWM signal S4 indicates the highlevel. The drive circuit 27 turns off the switching device 21 during aperiod in which the signal level of the PWM signal S4 indicates the lowlevel.

When the drive circuit 27 turns on the switching device 21, the DCvoltage of the DC power supply 1 is applied to the light source circuit3, and as a result the light emitting diodes 311 to 317 emit light.Specifically, when the switching device 21 is turned on, a voltage isapplied from the DC power supply 1 to a base of the transistor 322through the resistor 29, the diode 33, and the resistors 323 and 324 toturn on the transistor 322. As a result of turning on of the transistor322, a current flows through the light emitting diodes 311 to 317 toallow the light emitting diodes 311 to 317 to emit light. When thecurrent flows through the light emitting diodes 311 to 317, a voltage isgenerated across each resistor 325, 326. When the voltage across theresistor 325, 326 exceeds a threshold voltage of the transistor 321, thetransistor 321 is turned on. When the transistor 321 is turned on, abase voltage of the transistor 322 decreases to reach a thresholdvoltage, and as a result the transistor 322 is turned off. The lightemitting diodes 311 to 317 are turned off accordingly. When thetransistor 322 is turned off, the transistor 321 is turned off as well,leading to an application of a voltage to the base of the transistor 322to turn on the transistor 322. According to repetition of the aboveoperations, the current flowing through the light emitting diodes 311 to317 is kept constant.

When the drive circuit 27 turns off the switching device 21, the currentis inhibited from flowing through the light output circuit 3, and thelight emitting diodes 311 to 317 do not emit light.

With this operation, the rectangular wave voltage is applied from thelight output control device 2 to the light source circuit 3 to allow thelight source circuit 3 to emit light intermittently. Accordingly, thelight source circuit 3 emits light with the light output level indicatedby the light output control signal S3. Preferably, the frequency of thePWM signal S4 generated by the PWM signal generation circuit 26 is equalto or more than 500 Hz. When the PWM signal S4 has a frequency equal toor more than 500 Hz, a length of one cycle is 2 milliseconds or less,where one cycle includes a period in which the light emitting diodes 311to 317 emit light and a period in which the light emitting diodes 311 to317 do not emit light. That is, repetition cycle of the blinking of thelight emitting diodes 311 to 317 is smaller than 2 milliseconds. In thiscase, the blinking of the light emitted from the light emitting diodes311 to 317 cannot be recognized by the human, and the human feels thatthe light emitting diodes 311 to 317 emit light continuously.

When the PWM signal generation circuit 26 receives a light outputcontrol signal S3 indicating the setting value of 100% for light outputlevel from the signal selection circuit 25, the PWM signal generationcircuit 26 may output, to the drive circuit 27, a drive signal forkeeping the switching device 21 turned on. According to the drive signalsupplied from the PWM signal generation circuit 26, the drive circuit 27keeps the switching device 21 turned on. In this case, the light outputlevel of the light source circuit 3 is the maximum.

The switching device 21 serves as a switch for determining whether theDC voltage of the DC power supply 1 is supplied to the light sourcecircuit 3. Therefore, the light output control device 2 of the presentembodiment is smaller in a switching loss than the structure including achopper circuit, and has an improved efficiency. The DC voltage of theDC power supply 1 has a voltage value (DC 24 V, for example) allowingthe light source circuit 3 to emit light. Therefore, a smallerelectronic component having a low withstand voltage can be used for acircuit component such as the switching device 21 of the light outputcontrol device 2 in the present embodiment, compared to a configurationincluding a boost chopper circuit for increasing a voltage and astep-down chopper circuit for decreasing the boosted voltage to generatea voltage and supplying the stepped-down voltage to the light sourcecircuit 3. The light output control device 2 can be downsizedaccordingly.

(1.3) Structure of Light Output Control Device

FIG. 6 is an external perspective view of the light output controldevice 2. FIG. 7 is an exploded perspective view of the light outputcontrol device 2. The light output control device 2 includes a case 200made of metal. The case 200 includes a base plate 201 made of metal anda cover 202 made of metal. The base plate 201 has a U-shape when viewedin a longitudinal direction of the base plate 201. The cover 202 isattached to the base plate 201. A circuit board 250 is attached to thebase plate 201. The circuit board 250 is provided with a circuit shownin FIG. 1. Terminal bases 251 and 252 are mounted on a first end in thelongitudinal direction of the circuit board 250 and arranged side byside in a width direction of the circuit board 250 (see FIG. 7 and FIG.8). The terminal base 251 has a structure of a rapid-connectionterminal, and serves as the signal input port 230. The terminal base 252has a structure of a rapid-connection terminal, and serves as the signalinput port 240. Also, other terminal bases 253 and 254 are mounted on asecond end in the longitudinal direction of the circuit board 250 andarranged side by side in the width direction of the circuit board 250.The terminal base 253 has a structure of a rapid-connection terminal,and serves as the power supply connection port 210. The terminal base254 has a structure of a rapid-connection terminal, and serves as thelight source connection port 220.

The cover 202 covers a center region in the longitudinal direction ofthe circuit board 250. The first and second ends, on which the terminalbases 251 and 252 and the terminal bases 253 and 254 are mountedrespectively, of the circuit board 250 are not covered by the cover 202and exposed outside the cover 202. The terminal base 251 serving as thesignal input port 230 and the terminal base 252 serving as the signalinput port 240 are separate bodies in the embodiment. However, thesignal input port 230 and the signal input port 240 may be provided inone terminal base.

Three lead-type resistors 291 are mounted on the circuit board 250 andclose to the terminal base 253 serving as the power supply connectionport 210. The three resistors 291 constitute the resistor 29. The threeresistors 291 are connected in parallel to each other. An insulationsleeve 255 formed into a cylinder tube shape is mounted on the circuitboard 250 so as to surround the three resistors 291. An insulation sheet203 is attached to an inner face of the base plate 201. The insulationsheet 203 is made of synthetic resin with an electric insulationproperty, and is formed into a sheet shape. Also, a protection cover 204is attached to an upper side of the circuit board 250. The protectioncover 204 is made of synthetic resin with an electric insulationproperty. The protection cover 204 protects circuit components mountedon the circuit board 250 except for the terminal bases 251 to 254.

In the light output control device 2 of the present embodiment, thepower supply connection port 210 and the light source connection port220 are not dedicated connectors, but are terminal bases having astructure of rapid-connection terminal. Therefore, there is a concernthat a power supply wire connected to an AC power supply 100 may beaccidentally connected to the power supply connection port 210 and/orthe light source connection port 220. In this regard, in the presentembodiment, the resistor 29 is connected between the power supplyconnection port 210 and the light source connection port 220. Therefore,when the power supply wire connected to the AC power supply 100 isaccidentally connected to the power supply connection port 210 or thelight source connection port 220, the resistor(s) 291 will be fused andthus the circuit will be broken. As a result, other circuit componentscan be protected.

The resistor 291 having lead terminals is longer in an inter-terminaldistance than a chip-mount type resistor. Therefore, when the resistor291 is fused, arc discharge is not likely to occur between terminalselectrically connected to opposite ends of the resistor 291. It is thuspossible to ensure protection of the circuit. The inter-terminaldistance of the resistor 291 is defined as a distance between respectivepositions where opposite lead terminals of the resistor 291 are fixed tothe circuit board 250. Preferably, the inter-terminal distance is 5 mmor more.

The insulation sleeve 255 is provided on the circuit board 250 so as tosurround the resistors 291. Accordingly, fused parts of the resistors291 can be prevented from scattering outside the insulation sleeve 255.The light output control device 2 of the present embodiment includes thelead-type resistor 291 instead of a fuse. The lead-type resistor 291 issmaller in size and lower in cost than the fuse. Therefore, downsizingand cost reduction of the light output control device 2 can be achieved.The resistor 29 is electrically connected between the connectionterminal 211 of the power supply connection port 210 and the connectionterminal 221 of the light source connection port 220, but is not limitedthereto. For example, the resistor 29 may be electrically connectedbetween the connection terminal 212 and the connection terminal 222.

(1.4) Overview

As described above, the light output control device 2 of the presentembodiment includes the switching device 21, the multiple signal inputports (e.g., the two signal input ports 230 and 240 in the presentembodiment), the signal selection circuit 25, and the control circuit24. The switching device 21 is electrically connected between the DCpower supply 1 and the light source circuit 3 including thesemiconductor light emitting element (e.g., the light emitting diodes311 to 317 in the present embodiment). The multiple signal input portsrespectively correspond to multiple kinds of light output controlsignals. The signal selection circuit 25 selects any of two or morelight output control signals inputted through the multiple signal inputports. The control circuit 24 performs switching control of theswitching device 21 with a duty cycle corresponding to the light outputlevel indicated by the light output control signal selected by thesignal selection circuit 25. Each of the light output control signals isa signal indicating a maximum desired light output level for the lightsource circuit 3 when the magnitude of the light output control signalis minimum. The signal selection circuit 25 selects, from the two ormore light output control signals, a light output control signalindicating a lowest light output level.

With this configuration, when two or more light output control signalsare inputted to the signal selection circuit 25, the signal selectioncircuit 25 selects a light output control signal indicating a lowestlight output level from the two or more light output control signals.The control circuit 24 controls the light output of the light sourcecircuit 3 in accordance with the light output control signal selected bythe signal selection circuit 25. Therefore, the light output controldevice 2 can adequately handle the multiple kinds of light outputcontrol signals. In the present embodiment, the light output controldevice 2 includes the two signal input ports and the two kinds of lightoutput control signals are inputted to the signal selection circuit 25,but embodiments are not limited thereto. The light output control device2 may include three or more signal input ports, and the signal selectioncircuit 25 may receive three or more kinds of light output controlsignals through the signal input ports. The light output control signalS2 may be a voltage signal of which voltage level is any of three ormore levels. For example, the relay circuit 5 may include two or morerelays and output a voltage signal having any of three or more voltagelevels determined in accordance with a combination of on and off of thetwo or more relays. Accordingly, the second conversion circuit 50 may beconfigured to convert a voltage signal of which voltage level is any ofthree or more levels serving as the light output control signal S2 intothe conversion value having a voltage value corresponding to the voltagelevel of the received voltage signal. Examples of the multiple kinds oflight output control signals are not limited to the PWM signal and thevoltage signal of which voltage level is any of two or more levelsexemplified in the present embodiment, as long as the light controloutput signal is represented by a physical amount (such as a voltagevalue and a current value, for example) having a variable magnitude thatvaries with a desired light output level. The first conversion circuit40 and the second conversion circuit 50 each convert the light outputcontrol signal into a voltage value corresponding to the light outputlevel indicated by the light output control signal in the presentembodiment, but may convert it into a physical amount (current value,for example) other than the voltage value in another example.

The signal input port may be a component (a connector, for example) forbeing connected to an electric wire, or may be lead wires of anelectronic component or parts of electric conductors formed on thecircuit board as wiring, for example.

The illumination system of the present embodiment includes the lightoutput control device 2, the light source circuit 3 including thesemiconductor light emitting element (the light emitting diodes 311 to317 in the present embodiment).

With this configuration, it is possible to provide the illuminationsystem capable of adequately handling multiple kinds of light outputcontrol signals.

Embodiment 2

A light output control device and an illumination system according toEmbodiment 2 will be explained with reference to FIG. 9 to FIG. 11.

A light output control device 2 and an illumination system according tothe present embodiment have structures similar to those of the lightoutput control device 2 and the illumination system according toEmbodiment 1, except for a signal selection circuit 25. Therefore,components common to the present embodiment and those of Embodiment 1are designated by common reference signs and explanations thereof areomitted.

As shown in FIG. 9, the signal selection circuit 25 includes a firstconversion circuit 40, a second conversion circuit 80, a lower limitsetting circuit 60, and a zener diode 70 for setting an upper limit. Thefirst conversion circuit 40, the lower limit setting circuit 60, and thezener diode 70 have similar structures to those of Embodiment 1, andexplanations thereof are omitted. The circuit structure of the signalselection circuit 25 shown in FIG. 9 is an example, and the signalselection circuit 25 is not limited to having the circuit structureshown in FIG. 9.

For example, a dimmer 4 is connected to a signal input port 230 of thesignal selection circuit 25, and a relay circuit 5 is connected to asignal input port 240. A PWM signal (light output control signal S1)having a duty cycle corresponding to a desired light output level issupplied from the dimmer 4 to the signal input port 230. A voltagesignal (light output control signal S2) is supplied to the signal inputport 240. The light output control signal S2 is a voltage signal with avoltage level indicative of either of two levels in accordance withwhether a relay of the relay circuit 5 is on or off, for example.According to the light output control signal S1 of the presentembodiment, the light output control signal S1 indicates the maximumdesired light output level for the light source circuit 3 when the dutycycle (magnitude) of the light output control signal S1 is maximum.According to the light output control signal S2 of the presentembodiment, the light output control signal S2 indicates the maximumdesired light output level for the light source circuit 3 when thevoltage level (magnitude) of the light output control signal S2 ismaximum.

In the embodiment, the light output control signal S1 is a PWM signalhaving a duty cycle corresponding to a setting value for light outputlevel of the light source circuit 3. The light output control signal S1is defined to indicate the maximum of the setting value for light outputlevel when the duty cycle is maximum. FIG. 10A is a graph illustrating arelation between the setting value for light output level (desired lightoutput) and the duty cycle of the light output control signal S1. Thesetting value for light output level increases in direct proportion tothe duty cycle of the light output control signal S1. Therefore, thesetting value for light output level increases and also the light outputof the light source circuit 3 increases with an increase in the dutycycle of the light output control signal S1. In the example of FIG. 10A,the setting value for light output level changes linearly with respectto the duty cycle of the light output control signal S1, but the lightoutput controls signal S1 is not limited to this. The setting value forlight output level may change nonlinearly with respect to the duty cycleof the light output control signal S1, as long as the setting value forlight output level increases with an increase in the duty cycle.

The second conversion circuit 80 includes an NPN transistor 81, a PNPtransistor 82, resistors 83 to 86, an operation amplifier 87, and adiode 88. The operation amplifier 87 has a non-inverting input terminalconnected to a connection point of the resistors 85 and 86 thatconstitute a voltage divider circuit. The voltage divider circuit of theresistors 85 and 86 has a high voltage side terminal connected to acollector of the transistor 82. A constant DC voltage Vcc is suppliedfrom a power supply circuit 28 to an emitter of the transistor 82. Thevoltage divider circuit of the resistors 85 and 86 has a low voltageside terminal connected to a ground of the signal selection circuit 25.The transistor 82 has a base connected to a collector of the transistor81 through the resistor 84. The transistor 81 has an emitter connectedto the ground of the signal selection circuit 25. The transistor 81 hasa base connected to the signal input port 240 through the resistor 83.The operation amplifier 87 has an output terminal connected to an anodeof the diode 88. The operation amplifier 87 has an inverting inputterminal connected to a cathode of the diode 88. The cathode of thediode 88 is also connected to an output end P1 of the signal selectioncircuit 25. The diode 88 is connected between the output terminal of theoperation amplifier 87 and the output end P1 so as to allow a current toflow in a direction from the output terminal of the operation amplifier87 to the output end P1. Therefore, when a voltage value of the outputvoltage V1 of the first conversion circuit 40 is equal to or less than avoltage value of an output voltage V2 of the operation amplifier 87, thesecond conversion circuit 80 holds (clamps) the voltage value of theoutput end P1 to the voltage value of the output voltage V2 of theoperation amplifier 87.

In the present embodiment, the light output control signal S2 suppliedto the signal input port 240 is a voltage signal with a voltage levelindicative of either of two levels in accordance with whether the relayof the relay circuit 5 is on or off. The light output control signal S2is defined to indicate the maximum of the setting value for light outputlevel for the light source circuit 3 when the voltage level is maximum.FIG. 10B is a graph illustrating a relation between the light outputlevel and the voltage level of the light output control signal S2. Thelight output control signal S2 with the voltage level less thanthreshold Vth1 indicates the setting value of 0% for light output level.The light output control signal S2 with the voltage level equal to orhigher than the threshold Vth1 indicates the setting value of L1% forlight output level.

In the present embodiment, when the relay is turned on, the light outputcontrol signal S2 has a voltage level of VS1 (<Vth1), and the outputvoltage V2 of the operation amplifier 87 of the second conversioncircuit 80 thus has a voltage value indicating the setting value of 0%for light output level.

When the relay is turned off, the light output control signal S2 has avoltage level of VS2 (>Vth1), and the output voltage V2 of the operationamplifier 87 of the second conversion circuit 80 thus has a voltagevalue indicating the setting value of L1% for light output level. In theexample of FIG. 10B, the setting value for light output level isswitched between 0% and L1% depending on whether the voltage level ofthe light output control signal S2 is lower or higher than the thresholdVth1.

Note that, there may be a hysteresis width between the threshold for thelight output control signal S2 for determining whether to change thesetting value for light output level from L1% to 0% and the thresholdfor the light output control signal S2 for determining whether to changethe setting value for light output level from 0% to L1%.

Hereinafter, operations of the illumination system will be described.Operations of the control circuit 24 in the present embodiment aresimilar to those of Embodiment 1, and thus operations of the signalselection circuit 25 of Embodiment 2 different from that of Embodiment 1are explained hereinafter.

The following explanation referring to FIG. 11A and FIG. 11B relates toan operation of the signal selection circuit 25 with the signal inputport 230 and the signal input port 240 respectively receiving the lightoutput control signal S1 from the dimmer 4 and the light output controlsignal S2 from the relay circuit 5.

In a period from a time point t10 to a time point t12, the relay isturned on, and the light output control signal S2 has the first levelVS1. In this period, the light output level indicated by the lightoutput control signal S2 is 0%. In a period after the time point t12,the relay is turned off, and the light output control signal S2 has thesecond level VS2. In this period, the light output level indicated bythe light output control signal S2 is L1%.

At the time point t10, the duty cycle of the light output control signalS1 is set to 100%. The duty cycle of the light output control signal S1gradually decreases over time in a period between the time point t10 anda time point t13. The duty cycle of the light output control signal S1reaches 0% at the time point t13. Therefore, the light output levelindicated by the light output control signal S1 is 100% at the timepoint t10, and decreases from 100% to Lmin % with a lapse of time fromthe time point t11 to the time point t13.

In the period from the time point t10 to the time point t12, the lightoutput level indicated by the light output control signal S1 is higherthan the light output level indicated by the light output control signalS2. In this case, the voltage value of the output voltage V1 of thefirst conversion circuit 40 is greater than the voltage value of theoutput voltage V2 of the second conversion circuit 80, and as a resultthe voltage value of the output end P1 of the signal selection circuit25 is set to the voltage value of the output voltage V1 of the firstconversion circuit 40. That is, the signal selection circuit 25 selectsthe light output control signal S1, which indicates a higher lightoutput level of the light output control signals S1 and S2, andgenerates a light output control signal S3 in accordance with the lightoutput control signal S1, and outputs the light output control signal S3to the PWM signal generation circuit 26. In a period from the time pointt10 to a time point t11, the voltage value of the output voltage V1 ofthe first conversion circuit 40 is greater than the zener voltage VZ1 ofthe zener diode 70, and thus the light output control signal S3 is setto a voltage value corresponding to the upper limit (100%) of the lightoutput level. In a period from the time point t11 to the time point t12,the voltage value of the output voltage V1 of the first conversioncircuit 40 is smaller than the zener voltage VZ1, and thus the lightoutput control signal S3 is set to a voltage value corresponding to theoutput voltage V1 of the first conversion circuit 40.

The relay is turned off at the time point t12. In the period after thetime point t12, the light output level indicated by the light outputcontrol signal S1 is lower than the light output level indicated by thelight output control signal S2. In this case, the voltage value of theoutput voltage V2 of the second conversion circuit 80 is greater thanthe voltage value of the output voltage V1 of the first conversioncircuit 40, and as a result the voltage value of the output end P1 ofthe signal selection circuit 25 is set to the voltage value of theoutput voltage V2 of the second conversion circuit 80. The signalselection circuit 25 outputs the light output control signal S3 of whichvoltage value corresponds to the light output control signal S2.

In summary, when the two light output control signals S1 and S2 areinputted to the signal selection circuit 25, the signal selectioncircuit 25 selects a light output control signal indicating a higherlight output level from the two light output control signals S1 and S2.

In the explanation above, the two light output control signals S1 and S2are both inputted to the signal selection circuit 25, but either one ofthe light output control signals S1 and S2 alone may be inputted to thesignal selection circuit 25.

For example, the following explanation relates to an operation of thesignal selection circuit 25 in a case where the light output controlsignal S1 is supplied to the signal input port 230 but the light outputcontrol signals S2 is not supplied to the signal input port 240. Whenthe light output control signal S2 is not supplied to the signal inputport 240, the voltage level of the signal input port 240 is lower thanthe threshold Vth1. Therefore, the output voltage V2 of the operationamplifier 87 of the second conversion circuit 80 has a voltage valueindicating the setting value of 0% for light output level. In this case,the signal selection circuit 25 selects the output voltage V1, whichindicates a higher light output level, from the output voltages V1 andV2, and the signal selection circuit 25 outputs the light output controlsignal S3 having a voltage value corresponding to the light outputcontrol signal S1.

The following explanation relates to an operation of the signalselection circuit 25 in another case where the light output controlsignal S2 is supplied to the signal input port 240 but the light outputcontrol signals S1 is not supplied to the signal input port 230. It isconsidered that a situation where the light output control signal S1 isnot supplied to the signal input port 230 is equivalent to a situationwhere the light output control signal S1 having a duty cycle of 0% issupplied. Therefore, the output voltage V1 of the first conversioncircuit 40 has a voltage value indicating a minimum light output level.In the embodiment, due to the presence of the lower limit settingcircuit 60, the output voltage V1 is set to a voltage valuecorresponding to the lower limit Lmin. In this case, the signalselection circuit 25 selects the output voltage V2, which indicates ahigher light output level, from the output voltages V1 and V2, and thesignal selection circuit 25 outputs the light output control signal S3having a voltage value corresponding to the light output control signalS2.

As described above, the light output control device 2 of the presentembodiment includes the switching device 21, the multiple signal inputports (the two signal input ports 230 and 240 in the presentembodiment), the signal selection circuit 25, and the control circuit24. The switching device 21 is electrically connected between the DCpower supply 1 and the light source circuit 3 including thesemiconductor light emitting element (the light emitting diodes 311 to317 in the present embodiment). The multiple signal input portsrespectively correspond to multiple kinds of light output controlssignals. The signal selection circuit 25 selects any of two or morelight output control signals inputted through the multiple signal inputports. The control circuit 24 performs switching control of theswitching device 21 with a duty cycle corresponding to the light outputlevel indicated by the light output control signal selected by thesignal selection circuit 25. Each of the light output control signals isa signal indicating a maximum desired light output level for the lightsource circuit 3 when the magnitude of the light output control signalis maximum. The signal selection circuit 25 selects, from the two ormore light output control signals, a light output control signalindicating a highest light output level.

With this configuration, when two or more light output control signalsare inputted to the signal selection circuit 25, the signal selectioncircuit 25 selects a light output control signal indicating a highestlight output level from the two or more light output control signals.The control circuit 24 controls the light output of the light sourcecircuit 3 in accordance with the light output control signal selected bythe signal selection circuit 25. Therefore, the light output controldevice 2 can adequately handle the multiple kinds of light outputcontrol signals. In the present embodiment, the light output controldevice 2 includes the two signal input ports and the two kinds of lightoutput control signals are inputted to the signal selection circuit 25,but embodiments are not limited thereto. The light output control device2 may include three or more signal input ports, and the signal selectioncircuit 25 may receive three or more kinds of light output controlsignals through the signal input ports. The light output control signalS2 may be a voltage signal of which voltage level is any of three ormore levels. Accordingly, the second conversion circuit 50 may beconfigured to convert a voltage signal of which voltage level is any ofthree or more levels serving as the light output control signal S2 intothe conversion value having a voltage value corresponding to the voltagelevel of the received voltage signal. Examples of the multiple kinds oflight output control signals are not limited to the PWM signal and thevoltage signal of which voltage level is any of two or more levels, aslong as it is represented by a physical amount (such as a voltage valueand a current value, for example) having a variable magnitude thatvaries with a desired light output level. The first conversion circuit40 and the second conversion circuit 80 each convert the light outputcontrol signal into a voltage value corresponding to the light outputlevel indicated by the light output control signal in the presentembodiment, but may convert it into a physical amount (current value,for example) other than the voltage value in another example.

As described above, in the light output control device 2 of Embodiments1 and 2, the control circuit 24 performs the switching control of theswitching device 21 to convert the DC voltage supplied from the DC powersupply 1 into the rectangular wave voltage, and the resultantrectangular wave voltage is supplied to the light source circuit 3. Theamplitude of the resultant rectangular wave voltage equals to thevoltage value of the DC voltage supplied from the DC power supply 1.

The DC voltage supplied from the DC power supply 1 is converted into therectangular wave voltage having amplitude equal to a voltage value ofthe DC voltage by the switching operation of the switching device 21performed by the control circuit 24, and the resultant rectangular wavevoltage is applied to the light source circuit 3. That is, the switchingdevice 21 serves as a switch for determining whether the DC voltage ofthe DC power supply 1 is supplied to the light source circuit 3.Therefore, the light output control device 2 of the present embodimentis smaller in a switching loss than the structure including a choppercircuit, and has an improved efficiency.

The light output control device 2 of Embodiments 1 and 2 may furtherinclude the circuit board 250. The switching device 21, the multiplesignal input ports (the two signal input ports 230 and 240 in theembodiments), the signal selection circuit 25, and the control circuit24 are mounted on the circuit board 250. Each of the multiple signalinput ports may be disposed at an end of the circuit board 250.

In this case, since each of the multiple signal input terminals aredisposed at an end of the circuit board 250, it is easy to connectelectric wires thereto, compared to a case where the multiple signalinput ports are provided at a center of the circuit board 250.

In the light output control device 2 of Embodiment 1 and 2, preferably,at least one of the multiple kinds of light output control signals is asignal having a variable magnitude that varies continuously with adesired light output level of the light source circuit 3. In this case,it is possible to continuously adjust the light output level of thelight source circuit 3 by the light output control device 2.

Embodiment 3

The light output control device 2 and the light source circuit 3described in Embodiment 1 and 2 may be used in an illumination devicefor space illumination, a facility apparatus provided with a lightsource circuit for illumination, and the like. Examples of the facilityapparatus include a refrigeration showcase provided with a light sourcecircuit for illuminating commercial articles, a vending machine providedwith a light source circuit for illuminating articles or samples, andthe like.

A facility apparatus of the present embodiment is explained withreference to FIG. 12A.

The facility apparatus of the present embodiment is a refrigerationshowcase 90A. The refrigeration showcase 90A may be installed in aretail store such as a convenience store. The refrigeration showcase 90Ais used for displaying articles for sale while cooling or heating thearticles. The refrigeration showcase 90A includes a main body 91 thatincludes a display room 92 having an open front face. Multiple (three,in the illustrated example) display shelves 93 for displaying thearticles are provided in the display chamber 92. The light sourcecircuit 3 is provided in the main body 91 at a ceiling part of thedisplay room 92. A DC power supply 1 and the light output control device2 are installed inside the main body 91. The light output of the lightsource circuit 3 is controlled by the light output control device 2. Thearticles displayed on the display shelves 93 are illuminated with thelight emitted from the light source circuit 3.

A facility apparatus of a modification of the present embodiment isexplained with reference to FIG. 12B.

The facility apparatus of the modification is a vending machine 90B. Thevending machine 90B has a main body 94 including an inside space forminga display room 95 for displaying samples 96. A transparent window 97 isprovided in a front face of the main body 94, which allows a customer tosee the inside of the display room 95 through the window 97. The lightsource circuit 3 is provided in the main body 94 at an upper part of thedisplay room 95. A DC power supply 1 and the light output control device2 are installed inside the main body 94. The light output of the lightsource circuit 3 is controlled by the light output control device 2. Thesamples 96 displayed in the display room 95 are illuminated with thelight emitted from the light source circuit 3.

As described above, the facility apparatus (the refrigeration showcase90A the vending machine 90B) of the present embodiment includes thelight source circuit 3, the light output control device 2, and afacility apparatus body (main body 91, 94). The light source circuit 3includes a semiconductor light emitting element (light emitting diodes311 to 317, in the present embodiment). The light output control devicecontrols the light output of the light source circuit 3. The facilityapparatus body holds the light source circuit 3 and the light outputcontrol device 2.

With this configuration, it is possible to provide the facilityapparatus capable of adequately handling multiple kinds of light outputcontrol signals.

(Aspects)

As apparent from the embodiments described above, a light output controldevice (2) according to the first aspect includes a switching device(21), multiple signal input ports (230, 240), a signal selection circuit(25), and a control circuit (24). The switching device (21) is to beelectrically connected between a direct-current power supply (1) and alight source circuit (3). The light source circuit (3) includes asemiconductor light emitting element (311 to 317). The multiple signalinput ports (230 and 240) respectively correspond to multiple kinds oflight output control signals (S1, S2). The signal selection circuit (25)is configured to, when receiving two or more light output controlsignals (S1, S2) indicating different light output levels through themultiple signal input ports (230, 240), select a light output controlsignal indicating a lowest light output level, from the two or morelight output control signals (S1, S2). The control circuit (24) isconfigured to perform switching control of the switching device (21)with a duty cycle corresponding to the lowest light output levelindicated by the light output control signal selected by the signalselecting circuit (25).

The light output control device (2) according to the second aspect wouldbe realized in combination with the first aspect. In the second aspect,the signal selection circuit (25) includes multiple conversion circuits(40, 50) respectively corresponding to the multiple signal input ports(230, 240). Each of the multiple conversion circuits (40, 50) isconfigured to receive a light output control signal of the multiplekinds of light output control signals (S1, S2) through a correspondingone of the multiple signal input ports (230, 240), and convert thereceived light output control signal into a conversion value which isrepresented by a physical amount and has a magnitude corresponding to alight output level indicated by the received light output controlsignal. The signal selection circuit (25) is configured to select, fromthe two or more light output control signals (S1, S2), a light outputcontrol signal corresponding to the conversion value indicating thelowest light output level.

The light output control device (2) according to the third aspectincludes a switching device (21), multiple signal input ports (230,240), a signal selection circuit (25), and a control circuit (24). Theswitching device (21) is to be electrically connected between adirect-current power supply (1) and a light source circuit (3). Thelight source circuit (3) includes a semiconductor light emitting element(311 to 317). The multiple signal input ports (230, 240) respectivelycorrespond to multiple kinds of light output control signals (S1, S2).The signal selection circuit (25) is configured to, when receiving twoor more light output control signals (S1, S2) indicating different lightoutput levels through the multiple signal input ports, select a lightoutput control signal indicating a highest light output level, from thetwo or more light output control signals (S1, S2). The control circuit(24) is configured to perform switching control of the switching device(21) with a duty cycle corresponding to the highest light output levelindicated by the light output control signal selected by the signalselecting circuit (25).

The light output control device (2) according to the fourth aspect wouldbe realized in combination with the third aspect. In the fourth aspect,the signal selection circuit (25) includes multiple conversion circuits(40, 80) respectively corresponding to the multiple signal input ports(230, 240). Each of the multiple conversion circuits (40, 80) isconfigured to receive a light output control signal of the multiplekinds of light output control signals (S1, S2) through a correspondingone of the multiple signal input ports (230, 240), and convert thereceived light output control signal into a conversion value which isrepresented by a physical amount and has a magnitude corresponding to alight output level indicated by the received light output controlsignal. The signal selection circuit (25) is configured to select, fromthe two or more light output control signals (S1, S2), a light outputcontrol signal corresponding to the conversion value indicating thehighest light output level.

The light output control device (2) according to the fifth aspect wouldbe realized in combination with the second or fourth aspect. In thefifth aspect, the multiple conversion circuits (40, 50; 40, 80) includesthe first conversion circuit (40) and the second conversion circuit (50;80). The first conversion circuit (40) is configured to convert a pulsewidth modulation signal serving as one (S1) of the multiple kinds oflight output control signals (S1, S2) into the conversion value which isrepresented by a DC voltage and has a voltage value corresponding to aduty cycle of the received pulse width modulation signal. The secondconversion circuit (50; 80) is configured to convert a voltage signal ofwhich voltage level is any of two or more levels serving as one (S2) ofthe multiple kinds of light output control signals (S1, S2) into theconversion value having a voltage value corresponding to the voltagelevel of the received voltage signal.

The light output control device (2) according to the sixth aspect wouldbe realized in combination with any one of the first to fifth aspects.In the sixth aspect, the control circuit (24) is configured to performthe switching control of the switching device (21) to convert a DCvoltage outputted from the DC power supply (1) into a rectangular wavevoltage to supply the rectangular wave voltage to the light sourcecircuit (3). The rectangular wave voltage has an amplitude equal to avoltage value of the DC voltage outputted from the DC power supply (1).

The light output control device (2) according to the seventh aspectwould be realized in combination with any one of the first to sixthaspects, and further includes a circuit board (250). The switchingdevice (21), the multiple signal input ports (230, 240), the signalselection circuit (25), and the control circuit (24) are mounted on thecircuit board (250). Each of the multiple signal input ports (230, 240)is arranged on an end of the circuit board (250).

The light output control device (2) according to the eighth aspect wouldbe realized in combination with any one of the first to seventh aspects.In the eighth aspect, at least one of the multiple kinds of light outputcontrol signals (S1, S2) is a signal having a variable magnitude thatvaries continuously with a desired light output level of the lightsource circuit (3).

The illumination system according to the ninth aspect includes the lightoutput control device (2) according to any one of the first to eighthaspects, and the light source circuit (3) including the semiconductorlight emitting element (311 to 317).

The facility apparatus (90A, 90B) according to the tenth aspect includesthe light output control device (2) according to any one of the first toeighth aspects, the light source circuit (3), and a facility apparatusbody (91; 94). The light source circuit (3) includes the semiconductorlight emitting element (311 to 317). The facility apparatus body (91;94) holds the light source circuit (3) and the light output controldevice (2).

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that they may be appliedin numerous applications, only some of which have been described herein.It is intended by the following claims to claim any and allmodifications and variations that fall within the true scope of thepresent teachings.

1. A light output control device, comprising: a switching device to beelectrically connected between a direct-current power supply and a lightsource circuit including a semiconductor light emitting element;multiple signal input ports respectively corresponding to multiple kindsof light output control signals; a signal selection circuit configuredto, when receiving two or more light output control signals indicatingdifferent light output levels through the multiple signal input ports,select a light output control signal indicating a lowest light outputlevel, from the two or more light output control signals; and a controlcircuit configured to perform switching control of the switching devicewith a duty cycle corresponding to the lowest light output levelindicated by the light output control signal selected by the signalselecting circuit.
 2. The light output control device of claim 1,wherein: the signal selection circuit includes multiple conversioncircuits respectively corresponding to the multiple signal input ports,each of the multiple conversion circuits is configured to receive alight output control signal of the multiple kinds of light outputcontrol signals through a corresponding one of the multiple signal inputports, and convert the received light output control signal into aconversion value which is represented by a physical amount and has amagnitude corresponding to a light output level indicated by thereceived light output control signal, and the signal selection circuitis configured to select, from the two or more light output controlsignals, a light output control signal corresponding to the conversionvalue indicating the lowest light output level.
 3. The light outputcontrol device of claim 2, wherein: the multiple conversion circuitsinclude a first conversion circuit configured to convert a pulse widthmodulation signal serving as one of the multiple kinds of light outputcontrol signals into the conversion value which is represented by a DCvoltage and has a voltage value corresponding to a duty cycle of thereceived pulse width modulation signal, and a second conversion circuitconfigured to convert a voltage signal of which voltage level is any oftwo or more levels serving as one of the multiple kinds of light outputcontrol signals into the conversion value having a voltage valuecorresponding to the voltage level of the received voltage signal. 4.The light output control device of claim 1, wherein the control circuitis configured to perform the switching control of the switching deviceto convert a DC voltage outputted from the DC power supply into arectangular wave voltage to supply the rectangular wave voltage to thelight source circuit, the rectangular wave voltage having an amplitudeequal to a voltage value of the DC voltage outputted from the DC powersupply.
 5. The light output control device of claim 1, wherein theswitching device, the multiple signal input ports, the signal selectioncircuit, and the control circuit are mounted on a circuit board, andeach of the multiple signal input ports is arranged on an end of thecircuit board.
 6. The light output control device of claim 1, wherein atleast one of the multiple kinds of light output control signals is asignal having a variable magnitude that varies continuously with adesired light output level of the light source circuit.
 7. Anillumination system, comprising: the light output control device ofclaim 1; and the light source circuit including the semiconductor lightemitting element.
 8. A facility apparatus, comprising: the light outputcontrol device of claim 1; the light source circuit including thesemiconductor light emitting element; and a facility apparatus body thatholds the light source circuit and the light output control device.
 9. Alight output control device, comprising: a switching device to beelectrically connected between a direct-current power supply and a lightsource circuit including a semiconductor light emitting element;multiple signal input ports respectively corresponding to multiple kindsof light output control signals; a signal selection circuit configuredto, when receiving two or more light output control signals indicatingdifferent light output levels through the multiple signal input ports,select a light output control signal indicating a highest light outputlevel, from the two or more light output control signals; and a controlcircuit configured to perform switching control of the switching devicewith a duty cycle corresponding to the highest light output levelindicated by the light output control signal selected by the signalselecting circuit.
 10. The light output control device of claim 9,wherein the signal selection circuit includes multiple conversioncircuits respectively corresponding to the multiple signal input ports,each of the multiple conversion circuits is configured to receive alight output control signal of the multiple kinds of light outputcontrol signals through a corresponding one of the multiple signal inputports, and convert the received light output control signal into aconversion value which is represented by a physical amount and has amagnitude corresponding to a light output level indicated by thereceived light output control signal, and the signal selection circuitis configured to select, from the two or more light output controlsignals, a light output control signal corresponding to the conversionvalue indicating the highest light output level.
 11. The light outputcontrol device of claim 10, wherein: the multiple conversion circuitsinclude a first conversion circuit configured to convert a pulse widthmodulation signal serving as one of the multiple kinds of light outputcontrol signals into the conversion value which is represented by a DCvoltage and has a voltage value corresponding to a duty cycle of thereceived pulse width modulation signal, and a second conversion circuitconfigured to receive a voltage signal of which voltage level is any oftwo or more levels as one of the multiple light output control signalsinto the conversion value having a voltage value corresponding to thevoltage level of the received voltage signal.
 12. The light outputcontrol device of claim 9, wherein the control circuit is configured toperform the switching control of the switching device to convert a DCvoltage outputted from the DC power supply into a rectangular wavevoltage to supply the rectangular wave voltage to the light sourcecircuit, the rectangular wave voltage having an amplitude equal to avoltage value of the DC voltage outputted from the DC power supply. 13.The light output control device of claim 9, wherein the switchingdevice, the multiple signal input ports, the signal selection circuit,and the control circuit are mounted on a circuit board, and each of themultiple signal input ports is arranged on an end of the circuit board.14. The light output control device of claim 9, wherein at least one ofthe multiple kinds of light output control signals is a signal having avariable magnitude that varies continuously with a desired light outputlevel of the light source circuit.
 15. An illumination system,comprising: the light output control device of claim 9; and the lightsource circuit including the semiconductor light emitting element.
 16. Afacility apparatus, comprising: the light output control device of claim9; the light source circuit including the semiconductor light emittingelement; and a facility apparatus body that holds the light sourcecircuit and the light output control device.